package org.bouncycastle.crypto.engines;

import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.DataLengthException;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.RC2Parameters;

/**
 * an implementation of RC2 as described in RFC 2268
 * "A Description of the RC2(r) Encryption Algorithm" R. Rivest.
 */
public class RC2Engine implements BlockCipher {
    //
    // the values we use for key expansion (based on the digits of PI)
    //
    private static byte[] piTable = { (byte) 0xd9, (byte) 0x78, (byte) 0xf9,
            (byte) 0xc4, (byte) 0x19, (byte) 0xdd, (byte) 0xb5, (byte) 0xed,
            (byte) 0x28, (byte) 0xe9, (byte) 0xfd, (byte) 0x79, (byte) 0x4a,
            (byte) 0xa0, (byte) 0xd8, (byte) 0x9d, (byte) 0xc6, (byte) 0x7e,
            (byte) 0x37, (byte) 0x83, (byte) 0x2b, (byte) 0x76, (byte) 0x53,
            (byte) 0x8e, (byte) 0x62, (byte) 0x4c, (byte) 0x64, (byte) 0x88,
            (byte) 0x44, (byte) 0x8b, (byte) 0xfb, (byte) 0xa2, (byte) 0x17,
            (byte) 0x9a, (byte) 0x59, (byte) 0xf5, (byte) 0x87, (byte) 0xb3,
            (byte) 0x4f, (byte) 0x13, (byte) 0x61, (byte) 0x45, (byte) 0x6d,
            (byte) 0x8d, (byte) 0x9, (byte) 0x81, (byte) 0x7d, (byte) 0x32,
            (byte) 0xbd, (byte) 0x8f, (byte) 0x40, (byte) 0xeb, (byte) 0x86,
            (byte) 0xb7, (byte) 0x7b, (byte) 0xb, (byte) 0xf0, (byte) 0x95,
            (byte) 0x21, (byte) 0x22, (byte) 0x5c, (byte) 0x6b, (byte) 0x4e,
            (byte) 0x82, (byte) 0x54, (byte) 0xd6, (byte) 0x65, (byte) 0x93,
            (byte) 0xce, (byte) 0x60, (byte) 0xb2, (byte) 0x1c, (byte) 0x73,
            (byte) 0x56, (byte) 0xc0, (byte) 0x14, (byte) 0xa7, (byte) 0x8c,
            (byte) 0xf1, (byte) 0xdc, (byte) 0x12, (byte) 0x75, (byte) 0xca,
            (byte) 0x1f, (byte) 0x3b, (byte) 0xbe, (byte) 0xe4, (byte) 0xd1,
            (byte) 0x42, (byte) 0x3d, (byte) 0xd4, (byte) 0x30, (byte) 0xa3,
            (byte) 0x3c, (byte) 0xb6, (byte) 0x26, (byte) 0x6f, (byte) 0xbf,
            (byte) 0xe, (byte) 0xda, (byte) 0x46, (byte) 0x69, (byte) 0x7,
            (byte) 0x57, (byte) 0x27, (byte) 0xf2, (byte) 0x1d, (byte) 0x9b,
            (byte) 0xbc, (byte) 0x94, (byte) 0x43, (byte) 0x3, (byte) 0xf8,
            (byte) 0x11, (byte) 0xc7, (byte) 0xf6, (byte) 0x90, (byte) 0xef,
            (byte) 0x3e, (byte) 0xe7, (byte) 0x6, (byte) 0xc3, (byte) 0xd5,
            (byte) 0x2f, (byte) 0xc8, (byte) 0x66, (byte) 0x1e, (byte) 0xd7,
            (byte) 0x8, (byte) 0xe8, (byte) 0xea, (byte) 0xde, (byte) 0x80,
            (byte) 0x52, (byte) 0xee, (byte) 0xf7, (byte) 0x84, (byte) 0xaa,
            (byte) 0x72, (byte) 0xac, (byte) 0x35, (byte) 0x4d, (byte) 0x6a,
            (byte) 0x2a, (byte) 0x96, (byte) 0x1a, (byte) 0xd2, (byte) 0x71,
            (byte) 0x5a, (byte) 0x15, (byte) 0x49, (byte) 0x74, (byte) 0x4b,
            (byte) 0x9f, (byte) 0xd0, (byte) 0x5e, (byte) 0x4, (byte) 0x18,
            (byte) 0xa4, (byte) 0xec, (byte) 0xc2, (byte) 0xe0, (byte) 0x41,
            (byte) 0x6e, (byte) 0xf, (byte) 0x51, (byte) 0xcb, (byte) 0xcc,
            (byte) 0x24, (byte) 0x91, (byte) 0xaf, (byte) 0x50, (byte) 0xa1,
            (byte) 0xf4, (byte) 0x70, (byte) 0x39, (byte) 0x99, (byte) 0x7c,
            (byte) 0x3a, (byte) 0x85, (byte) 0x23, (byte) 0xb8, (byte) 0xb4,
            (byte) 0x7a, (byte) 0xfc, (byte) 0x2, (byte) 0x36, (byte) 0x5b,
            (byte) 0x25, (byte) 0x55, (byte) 0x97, (byte) 0x31, (byte) 0x2d,
            (byte) 0x5d, (byte) 0xfa, (byte) 0x98, (byte) 0xe3, (byte) 0x8a,
            (byte) 0x92, (byte) 0xae, (byte) 0x5, (byte) 0xdf, (byte) 0x29,
            (byte) 0x10, (byte) 0x67, (byte) 0x6c, (byte) 0xba, (byte) 0xc9,
            (byte) 0xd3, (byte) 0x0, (byte) 0xe6, (byte) 0xcf, (byte) 0xe1,
            (byte) 0x9e, (byte) 0xa8, (byte) 0x2c, (byte) 0x63, (byte) 0x16,
            (byte) 0x1, (byte) 0x3f, (byte) 0x58, (byte) 0xe2, (byte) 0x89,
            (byte) 0xa9, (byte) 0xd, (byte) 0x38, (byte) 0x34, (byte) 0x1b,
            (byte) 0xab, (byte) 0x33, (byte) 0xff, (byte) 0xb0, (byte) 0xbb,
            (byte) 0x48, (byte) 0xc, (byte) 0x5f, (byte) 0xb9, (byte) 0xb1,
            (byte) 0xcd, (byte) 0x2e, (byte) 0xc5, (byte) 0xf3, (byte) 0xdb,
            (byte) 0x47, (byte) 0xe5, (byte) 0xa5, (byte) 0x9c, (byte) 0x77,
            (byte) 0xa, (byte) 0xa6, (byte) 0x20, (byte) 0x68, (byte) 0xfe,
            (byte) 0x7f, (byte) 0xc1, (byte) 0xad };

    private static final int BLOCK_SIZE = 8;

    private int[] workingKey;
    private boolean encrypting;

    private int[] generateWorkingKey(byte[] key, int bits) {
        int x;
        int[] xKey = new int[128];

        for (int i = 0; i != key.length; i++) {
            xKey[i] = key[i] & 0xff;
        }

        // Phase 1: Expand input key to 128 bytes
        int len = key.length;

        if (len < 128) {
            int index = 0;

            x = xKey[len - 1];

            do {
                x = piTable[(x + xKey[index++]) & 255] & 0xff;
                xKey[len++] = x;
            } while (len < 128);
        }

        // Phase 2 - reduce effective key size to "bits"
        len = (bits + 7) >> 3;
        x = piTable[xKey[128 - len] & (255 >> (7 & -bits))] & 0xff;
        xKey[128 - len] = x;

        for (int i = 128 - len - 1; i >= 0; i--) {
            x = piTable[x ^ xKey[i + len]] & 0xff;
            xKey[i] = x;
        }

        // Phase 3 - copy to newKey in little-endian order
        int[] newKey = new int[64];

        for (int i = 0; i != newKey.length; i++) {
            newKey[i] = (xKey[2 * i] + (xKey[2 * i + 1] << 8));
        }

        return newKey;
    }

    /**
     * initialise a RC2 cipher.
     * 
     * @param encrypting
     *            whether or not we are for encryption.
     * @param params
     *            the parameters required to set up the cipher.
     * @exception IllegalArgumentException
     *                if the params argument is inappropriate.
     */
    public void init(boolean encrypting, CipherParameters params) {
        this.encrypting = encrypting;

        if (params instanceof RC2Parameters) {
            RC2Parameters param = (RC2Parameters) params;

            workingKey = generateWorkingKey(param.getKey(),
                    param.getEffectiveKeyBits());
        } else if (params instanceof KeyParameter) {
            byte[] key = ((KeyParameter) params).getKey();

            workingKey = generateWorkingKey(key, key.length * 8);
        } else {
            throw new IllegalArgumentException(
                    "invalid parameter passed to RC2 init - "
                            + params.getClass().getName());
        }

    }

    public void reset() {
    }

    public String getAlgorithmName() {
        return "RC2";
    }

    public int getBlockSize() {
        return BLOCK_SIZE;
    }

    public final int processBlock(byte[] in, int inOff, byte[] out, int outOff) {
        if (workingKey == null) {
            throw new IllegalStateException("RC2 engine not initialised");
        }

        if ((inOff + BLOCK_SIZE) > in.length) {
            throw new DataLengthException("input buffer too short");
        }

        if ((outOff + BLOCK_SIZE) > out.length) {
            throw new DataLengthException("output buffer too short");
        }

        if (encrypting) {
            encryptBlock(in, inOff, out, outOff);
        } else {
            decryptBlock(in, inOff, out, outOff);
        }

        return BLOCK_SIZE;
    }

    /**
     * return the result rotating the 16 bit number in x left by y
     */
    private int rotateWordLeft(int x, int y) {
        x &= 0xffff;
        return (x << y) | (x >> (16 - y));
    }

    private void encryptBlock(byte[] in, int inOff, byte[] out, int outOff) {
        int x76, x54, x32, x10;

        x76 = ((in[inOff + 7] & 0xff) << 8) + (in[inOff + 6] & 0xff);
        x54 = ((in[inOff + 5] & 0xff) << 8) + (in[inOff + 4] & 0xff);
        x32 = ((in[inOff + 3] & 0xff) << 8) + (in[inOff + 2] & 0xff);
        x10 = ((in[inOff + 1] & 0xff) << 8) + (in[inOff + 0] & 0xff);

        for (int i = 0; i <= 16; i += 4) {
            x10 = rotateWordLeft(x10 + (x32 & ~x76) + (x54 & x76)
                    + workingKey[i], 1);
            x32 = rotateWordLeft(x32 + (x54 & ~x10) + (x76 & x10)
                    + workingKey[i + 1], 2);
            x54 = rotateWordLeft(x54 + (x76 & ~x32) + (x10 & x32)
                    + workingKey[i + 2], 3);
            x76 = rotateWordLeft(x76 + (x10 & ~x54) + (x32 & x54)
                    + workingKey[i + 3], 5);
        }

        x10 += workingKey[x76 & 63];
        x32 += workingKey[x10 & 63];
        x54 += workingKey[x32 & 63];
        x76 += workingKey[x54 & 63];

        for (int i = 20; i <= 40; i += 4) {
            x10 = rotateWordLeft(x10 + (x32 & ~x76) + (x54 & x76)
                    + workingKey[i], 1);
            x32 = rotateWordLeft(x32 + (x54 & ~x10) + (x76 & x10)
                    + workingKey[i + 1], 2);
            x54 = rotateWordLeft(x54 + (x76 & ~x32) + (x10 & x32)
                    + workingKey[i + 2], 3);
            x76 = rotateWordLeft(x76 + (x10 & ~x54) + (x32 & x54)
                    + workingKey[i + 3], 5);
        }

        x10 += workingKey[x76 & 63];
        x32 += workingKey[x10 & 63];
        x54 += workingKey[x32 & 63];
        x76 += workingKey[x54 & 63];

        for (int i = 44; i < 64; i += 4) {
            x10 = rotateWordLeft(x10 + (x32 & ~x76) + (x54 & x76)
                    + workingKey[i], 1);
            x32 = rotateWordLeft(x32 + (x54 & ~x10) + (x76 & x10)
                    + workingKey[i + 1], 2);
            x54 = rotateWordLeft(x54 + (x76 & ~x32) + (x10 & x32)
                    + workingKey[i + 2], 3);
            x76 = rotateWordLeft(x76 + (x10 & ~x54) + (x32 & x54)
                    + workingKey[i + 3], 5);
        }

        out[outOff + 0] = (byte) x10;
        out[outOff + 1] = (byte) (x10 >> 8);
        out[outOff + 2] = (byte) x32;
        out[outOff + 3] = (byte) (x32 >> 8);
        out[outOff + 4] = (byte) x54;
        out[outOff + 5] = (byte) (x54 >> 8);
        out[outOff + 6] = (byte) x76;
        out[outOff + 7] = (byte) (x76 >> 8);
    }

    private void decryptBlock(byte[] in, int inOff, byte[] out, int outOff) {
        int x76, x54, x32, x10;

        x76 = ((in[inOff + 7] & 0xff) << 8) + (in[inOff + 6] & 0xff);
        x54 = ((in[inOff + 5] & 0xff) << 8) + (in[inOff + 4] & 0xff);
        x32 = ((in[inOff + 3] & 0xff) << 8) + (in[inOff + 2] & 0xff);
        x10 = ((in[inOff + 1] & 0xff) << 8) + (in[inOff + 0] & 0xff);

        for (int i = 60; i >= 44; i -= 4) {
            x76 = rotateWordLeft(x76, 11)
                    - ((x10 & ~x54) + (x32 & x54) + workingKey[i + 3]);
            x54 = rotateWordLeft(x54, 13)
                    - ((x76 & ~x32) + (x10 & x32) + workingKey[i + 2]);
            x32 = rotateWordLeft(x32, 14)
                    - ((x54 & ~x10) + (x76 & x10) + workingKey[i + 1]);
            x10 = rotateWordLeft(x10, 15)
                    - ((x32 & ~x76) + (x54 & x76) + workingKey[i]);
        }

        x76 -= workingKey[x54 & 63];
        x54 -= workingKey[x32 & 63];
        x32 -= workingKey[x10 & 63];
        x10 -= workingKey[x76 & 63];

        for (int i = 40; i >= 20; i -= 4) {
            x76 = rotateWordLeft(x76, 11)
                    - ((x10 & ~x54) + (x32 & x54) + workingKey[i + 3]);
            x54 = rotateWordLeft(x54, 13)
                    - ((x76 & ~x32) + (x10 & x32) + workingKey[i + 2]);
            x32 = rotateWordLeft(x32, 14)
                    - ((x54 & ~x10) + (x76 & x10) + workingKey[i + 1]);
            x10 = rotateWordLeft(x10, 15)
                    - ((x32 & ~x76) + (x54 & x76) + workingKey[i]);
        }

        x76 -= workingKey[x54 & 63];
        x54 -= workingKey[x32 & 63];
        x32 -= workingKey[x10 & 63];
        x10 -= workingKey[x76 & 63];

        for (int i = 16; i >= 0; i -= 4) {
            x76 = rotateWordLeft(x76, 11)
                    - ((x10 & ~x54) + (x32 & x54) + workingKey[i + 3]);
            x54 = rotateWordLeft(x54, 13)
                    - ((x76 & ~x32) + (x10 & x32) + workingKey[i + 2]);
            x32 = rotateWordLeft(x32, 14)
                    - ((x54 & ~x10) + (x76 & x10) + workingKey[i + 1]);
            x10 = rotateWordLeft(x10, 15)
                    - ((x32 & ~x76) + (x54 & x76) + workingKey[i]);
        }

        out[outOff + 0] = (byte) x10;
        out[outOff + 1] = (byte) (x10 >> 8);
        out[outOff + 2] = (byte) x32;
        out[outOff + 3] = (byte) (x32 >> 8);
        out[outOff + 4] = (byte) x54;
        out[outOff + 5] = (byte) (x54 >> 8);
        out[outOff + 6] = (byte) x76;
        out[outOff + 7] = (byte) (x76 >> 8);
    }
}